1. Technical Field
The present invention relates to a droplet discharge apparatus.
2. Related Art
A droplet discharge apparatus for discharging a liquid in the form of droplets is known as an apparatus for forming a desired pattern on a substrate. A droplet discharge apparatus includes a substrate placed on a stage and a droplet discharge head for discharging a liquid in the form of droplets, and forms a pattern by disposing droplets discharged from the droplet discharge head in desired positions on the substrate while the droplet discharge head scans the substrate.
In order to form a high-resolution pattern on a substrate using a droplet discharge apparatus, the amounts of droplets discharged from nozzles of the droplet discharge head must be highly uniform. For this reason, a pressure control valve is provided between an ink tank for storing a liquid and a droplet discharge head in the droplet discharge apparatus so that the pressure applied to the liquid to be supplied to each droplet discharge head is controlled. As a configuration for providing such a pressure control valve, JP-A-09-277561 proposes that a pressure control valve be directly connected to a droplet discharge head so that the size of the apparatus is reduced.
Incidentally, in a large-scale, industrial droplet discharge apparatus used when manufacturing large display panels or the like, multiple droplet discharge heads are disposed on one carriage so as to reduce the frequency with which a large substrate is scanned. In order for each droplet discharge head mounted on the carriage to draw a fine pattern of several tens of micrometers, the relative positions among the droplet discharge heads and the positions of the droplet discharge heads relative to the carriage must be highly accurate.
In order to obtain such position accuracy when mounting the above-mentioned droplet discharge heads on the carriage, first, the positions of the droplet discharge heads relative to the carriage are optically detected and then the positions of the droplet discharge heads are fine-tuned on the basis of the detected positions. If the positions of the droplet discharge heads and the corresponding target positions are optically matched, the droplet discharge heads and the carriage are instantly bonded together using an adhesive material.
On the other hand, if the droplet discharge head described in JP-A-09-277561 is mounted on a carriage, a pressure control valve is directly connected to the droplet discharge head. Accordingly, the load imposed on the droplet discharge head is increased. This makes it difficult to fine-tune the position of the droplet discharge head. Also, the adhesiveness between the droplet discharge head and carriage is significantly deteriorated. Accordingly, the droplet discharge head is significantly displaced from the target position. In order to prevent such displacements of the droplet discharge heads in the above-mentioned large-scale, industrial droplet discharge apparatus, the droplet discharge head and corresponding pressure control valves must be separated.
However, if the droplet discharge heads and corresponding pressure control valves are separated, the pressures applied to a liquid are dropped in tubes connecting the outlets of the pressure control valves and the inlets of the corresponding droplet discharge heads. Accordingly, the supply pressure of the liquid to each droplet discharge head varies with tubes. While it seems that such a problem can be solved by equalizing the distances between the outlets of the pressure control valves and inlets of the corresponding droplet discharge heads, the size of the apparatus is increased, since the positions of the droplet discharge heads and the positions of the pressure control valves are significantly restricted.